"There is no one else — she's the whole plan," Sarah Kovner, a top Democratic fundraiser, told the paper. "She is by far the most experienced and qualified person we could possibly nominate. Not even on the horizon but on the far horizon."

These worries have been amplified by Clinton's recent stumbles as she faces the growing controversy over her use of a private email address while she was secretary of state.

"Anytime you have all your eggs in one basket, it is a concern," Delaware Gov. Jack Markell (D) told The Times.

The concerns are not just based on Clinton's controversial actions, but her operation's reaction to them as well. Her camp has been careening from one strategy to another since last week, when it was revealed she exclusively used a personal email address as secretary of state, reportedly breaking federal rules and leaving sensitive communications vulnerable to hackers.

"Had this story been responded to in two or three days instead of in eight days, it would not be as big," Robert Gibbs, a former Obama spokesman, told The Post. "They are the ones who put air in this balloon in a way that was not necessary at all. ... It's clear they lack an apparatus. She's a candidate without a campaign."

A 2008 presidential debate.
AP/Charlie Neibergall

One potential Clinton rival, former Maryland Gov. Martin O'Malley (D), questioned the premise of The Times story. Asked about it on MSNBC's "Morning Joe" on Thursday, O'Malley questioned the idea Clinton is the party's only viable option by pointing to her 2008 presidential bid, in which she was often branded as "inevitable" before losing to then-Sen. Barack Obama.

"Well maybe that's the way it is today," he said. "Most years, there's the 'inevitable front-runner.' And that 'inevitable front-runner' is inevitable right up until he or she is no longer inevitable. So I think you're going to see a robust conversation in the Democratic Party."

However, Clinton was far more vulnerable electorally in 2008 than she is today. In polls, fundraising, and top-tier supporters, Obama and even former Sen. John Edwards (D-North Carolina), the party's 2004 vice presidential nominee, were much better positioned to challenge Clinton then than any Democrat is now. Sen. Elizabeth Warren (D-Massachusetts), who said she's not going to run but would arguably be the most credible non-Clinton contender, trails Clinton by more than 40 points.

For their part, Republicans are clearly relishing the Democrats' Clinton dilemma.

"I am struck by the vast difference between the Republican and Democratic candidates," Cody Hoefert, co-chair of the Iowa Republican Party, remarked in February. "Republicans have a vibrant field of candidates with diverse strengths and backgrounds. The Democrats have only one real candidate."